Labor Trigger Biological Mystery

Doctors know a great deal about how labor and childbirth unfolds, but they still have not pinned down one single switch that definitively starts it. Research points to a complex cascade involving the fetus, placenta, uterus, hormones, inflammation, and prostaglandins, with theories including a placental clock and fetal signals from the maturing lungs. But no single trigger has been confirmed as the universal answer for every pregnancy.

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